Optical fiber termination coating dispenser

ABSTRACT

A dispenser for dispensing an index matching coating material onto an end of an optical fiber to be terminated includes a reservoir formed by a floor and sidewalls with a small portion of the index matching coating material being disposed on a top surface of the floor. An interior perimeter shape of the sidewalls is registrable with an external perimeter shape of an optical fiber contact to which the optical fiber is secured which allows the index matching material to be conveniently disposed on an end of the optical fiber by simply inserting the optical fiber contact into the reservoir.

BACKGROUND OF THE INVENTION

The present invention relates to articles and methods for disposing acoating material onto an end of an optical fiber to be terminated.

Optical fiber is widely being deployed for information transferapplications and in a variety of sensor applications. A commonrequirement in the optical fiber industry is to provide efficient andconvenient methods of connecting an optical fiber to either a lightsource, a light detector, another optical fiber, an optical fibercoupler, etc. A common method previously proposed is to simply leave anair gap between an end of the optical fiber being terminated and itsmating optical element, and this method is disadvantageous since lightis required to pass from the optical fiber core, into air and then intoa mating optical element (e.g. another fiber core). A difference in theindices of refraction between these adjacent materials (core, air, core)causes Fresnel reflections to be created at medium interfaces, and thesereflections generate noise as well as excessive optical losses.

Another method for terminating an optical fiber requires that the fiberbe disposed in physical contact with its optical element, this methodbeing disadvantageous since the fiber end must be carefully polished toachieve acceptable throughput losses as well as to eliminatereflections. Also, the fiber end can subsequently be damaged ifsubjected to vibrations or during numerous mating cycles.

Oils and greases have also been proposed to be disposed in contact withan optical fiber termination so as to create a uniform index ofrefraction medium for the light to travel through across an opticalfiber connection, however, all such methods are disadvantageous sinceconvenient methods of applying the grease or oil have yet to beproposed.

Finally, it has also been proposed to dispose elastic materials on anend of an optical fiber contact for creating an index matching mediumthrough which the light can pass. Specifically, U.S. Pat. No. 4,512,630discloses a method whereby an applicator tip is disposed in a liquid andthen retracted so as to hold a drop of the liquid which is then appliedto an end of an optical fiber contact. The liquid is then cured on thecontact end. Again, this method is disadvantageous since it is quitecraft sensitive to implement, especially by unskilled workers in thefield, and it also tends to be messy. In addition, it is also difficultto cure the liquid subsequent to application.

Another previously disclosed method for disposing an index matchingsolid substance onto an end of an optical fiber is disclosed in U.S.Pat. No. 4,436,366, this patent teaching disposing an appropriate indexmatching layer coating on a substrate film, then drying the coating, andthen covering the coating with a protective layer. In use, theprotective layer is stripped from the coating and an optical fibercontact is disposed in contact with the coating while simultaneouslycross-linking the coating so as to allow it to adhere to the opticalfiber contact end. Again, the disadvantage with this technique is thatit is not easily implemented by relatively unskilled workers, and henceit is not convenient or economical to use in practice.

The methods of both of these patents are further disadvantageous sincethe fiber coatings produced are permanently applied to the fibers whichallows the coatings to become contaminated or physically damaged, inwhich case new fiber terminations need to be prepared.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an optical fibercoating material dispenser which eliminates the above-noted drawbacks.

Specifically, one object of the invention is to provide an optical fibercoating material dispenser which is easy to make and which has avirtually unlimited shelf life.

It is a further object of the invention to provide an optical fibercoating material dispenser which is extremely craft friendly to use,even by relatively unskilled personnel, and which is yet quite effectivein applying a coating material onto an optical fiber end which isfunctionally superior to coating material application methods previouslyproposed.

These and other objects of the invention are achieved by an opticalfiber coating material dispenser which includes a reservoir formed in asubstrate, the reservoir including a coating material on a top surfaceof a reservoir floor which is preferably positioned so as to beprecisely located on the reservoir floor relative to sidewalls of thereservoir such that when an optical fiber contact having an opticalfiber therein is inserted into the reservoir such that side surfaces ofthe contact register with the reservoir sidewalls the coating materialis accurately positioned on the end of the optical fiber. The coatingmaterial can be either a liquid, a grease, or an elastic material,though elastic materials are most preferred since elastic materials aremost easily removed from optical fiber connectors and hence facilitatecleaning of such connectors. Preferably, the coating materialpreferentially adheres to the end of the optical fiber rather than thereservoir floor to facilitate application of the coating material ontothe end of the optical fiber. Another advantageous feature of theinvention is the use of a transparent reservoir floor which facilitatesplacement of the coating material on the top of the reservoir floorduring manufacturing and also aids in confirming accurate andappropriate placement of the coating material onto the end of theoptical fiber. The dispenser also preferably includes means for firstcleaning the optical fiber end prior to disposing the coating materialthereon.

It is yet a further object of the invention to provide a dispenser fordispensing a coating material onto an end of an optical fiber,comprising:

means for dispensing an optical fiber coating material, the dispensingmeans including a base and sidewalls surrounding the base so as to forman optical fiber coating material dispensing platform; and

an optical fiber end coating material disposed on the platform andseparated from the sidewalls.

The invention further includes preferred methods of making the opticalfiber coating material dispenser, methods of using the dispenser, and anoptical fiber contact formed by disposing a coating material on an endof an optical fiber secured therewithin utilizing the teachings of theinvention.

These and other objects of the invention will be more apparent byreference to the accompanying drawings and detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a plurality of optical fiber coatingmaterial dispensers according to the invention;

FIGS. 2-4 are sequential drawings showing a preferred method of applyinga coating material onto an end of an optical fiber;

FIG. 5 is a plan view of an optical fiber contact having a coatingmaterial on an end of an optical fiber secured to a mating opticalelement;

FIGS. 6-8 are sequential views of one preferred method of making thedispenser of the invention; and

FIG. 9 is a view of a multiple optical fiber contact termination for usewith the present invention.

FIG. 10 is a schematic side view illustrating use of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A first preferred embodiment of the invention will be explained byreference to FIG. 1. Referring to this figure, a coating dispenser 1includes a substrate 2 which has formed therein a cavity or reservoir 3which includes a reservoir floor 5 and a reservoir sidewall 6, thesidewall 6 being cylindrical in the embodiment illustrated. A coatingmaterial 8 is disposed on a top surface of the reservoir floor 5, asillustrated, and the reservoir 3 is preferably sealed by cover 10 havinga tab 11, the cover having a perimeter secured to a top surface of thesidewall 6.

Preferably, an inside perimeter shape of the sidewall 6 is complementaryto an outside perimeter shape of an optical fiber contact 14 (FIG. 2) onwhich the coating material 8 is to be disposed such that these surfacesare registrable, one with the other, so that when the contact isinserted into the reservoir 3 the coating material is oriented so as tocome in contact with an end 12 of an optical fiber core and, if desired,the cladding of the fiber, the fiber being secured to the optical fibercontact.

FIGS. 2-4 ilustrate sequential steps of applying the coating material 8onto the end 12 of the optical fiber 13 which is secured to the opticalfiber contact 14. Specifically, as FIG. 2 illustrates, the optical fibercontact is guided into the reservoir 3 by the sidewall 6, whichpreferably includes outward tapers 16 near an upper surface thereof soas to facilitate contact insertion therein.

FIG. 3 illustrates a fiber insertion state where the contact 14 has beentotally inserted into the reservoir 3 such that the coating material 8comes in contact with the fiber end 12. Thereafter, as FIG. 4illustrates, the contact 14 is removed from the reservoir 3. Accordingto the invention, a top surface of the reservoir floor 5, the opticalfiber end 12, and the coating material 8 are formed of materials suchthat the coating material 8 preferentially adheres to the optical fiberend 12 rather than the top surface of the reservoir floor 5.Accordingly, as FIG. 4 illustrates, upon removal of the contact from thereservoir, the coating material 8 adheres to the optical fiber end 12.

The contact 14 with the optical fiber end so coated can then be insertedinto any one of an innumerable variety of connectors, with the coatingmaterial 8 being available for creating a continuous index matchingmedium for light to travel through between the optical fiber 13 and amating optical element. This is most clearly illustrated in figure 5whereby first and second optical fiber contacts are shown in confrontingabutting relationship, held together by a connector assembly 15, detailsof which are not necessary for purposes of description of the inventionherein, with the gel ball 8 being squeezed between ends of the opticalfibers being connected.

According to the invention, each optical fiber 13 being terminated canhave its own coating material disposed thereon such that for everyconnection two coating materials are involved and mated together, thoughpreferably it is advantageous that only one coating material be disposedon only one of the optical fibers being terminated, so long as asufficient volume of coating material is provided so that an entiresurface of the optical fiber ends are adequately coated.

FIGS. 6-8 illustrate one preferred method of making the coating materialdispenser 1. Preferably, the floor 5 of the reservoir 3 is made of anelastic membrane which is piercable and self-healing when pierced with asmall diameter object (e.g. diameter less than 300 um). With the floor 5so constructed, as FIGS. 6 and 7 illustrate, a needle 16, such as ahypodermic needle or similar type of structure, can be used to piercethe membrane 5, the needle being hollow and containing an appropriatecoating material therein. Accordingly, when the reservoir floor 5 ispierced from below, a premeasured quantity of the coating material canbe ejected from an end of the needle 16 as illustrated in FIG. 7.Thereafter, upon withdrawal of the needle 16 from the reservoir 3, anelasticity of the reservoir floor 5 tears the coating material from theneedle 16 and results in the premeasured amount of coating materialbeing disposed in an appropriate location on the reservoir floor 5.

According to the invention, an exact location of the coating material 8is determined by appropriate registration of the bottom surface of thereservoir floor 5. This method of making the coating material dispenseris advantageous since it is quite simple to dispose an elastic gel typecoating material within the reservoir 3 using this method, even when thegel material possesses its elastic properties within the hypodermicneedle 16 since the elastic membrane is able to pierce the gel materialupon withdrawal of the needle 16 from the reservoir floor 5.Accordingly, one can fill the hypodermic needle with an appropriatematerial in liquid form and thereafter elasticize the material by anyappropriate means, e.g. by cross-linking by using heat, radiation, etc.Thereafter, the elastic material is easily dispensed and placed withinthe reservoir 3 as described by reference to FIGS. 6-8.

An alternative method of making a coating material dispenser of theinvention is to dispose the coating material onto the reservoir floor 5from above by utilizing any appropriate applicator, such as a hypodermicneedle as described or a solid needle which has been dipped into anappropriate coating material which adheres thereto due to surfacetension effects. According to this embodiment, the coating materialpreferably is placed on the reservoir floor in liquid form to ease itsplacement on the reservoir floor 5, and if a gel type coating materialis ultimately desired, the coating material could then be cross-linkedwithin the reservoir 3.

A preferred embodiment of the invention includes a coating material 8which is elastic, as opposed to a nonelastic material such as a grease.Preferably, the elastic coating material has an ultimate elongation inexcess of 20%, preferably in excess of 40%, more preferably in excess of100%, e.g. in excess of 200% and possibly even 500%. A cone penetrationof the elastic coating material 8 is preferably between 30 and 350 (10⁻¹mm), more preferably between 100 and 350 (10⁻¹ mm), more preferablybetween 200 and 300 (10⁻¹ mm) e.g. about 220 (10⁻¹ mm). Examples ofsuitable coating materials having properties as described are describedin U.S. Pat. Nos. 4,634,207 and 4,600,261 and U.S. application Ser. No.859,162 filed May 2, 1986, now abandoned, assigned to the assignee ofthe invention, the disclosures of which are incorporated herein byreference.

According to an alternate preferred embodiment, the coating material 8can comprise a liquid or grease material which does not possess anysignificant ultimate elongation or cone penetration values. Though sucha material is easily disposed within the reservoir and applied to an endof an optical fiber, as described, a drawback of such a material is thatit cannot be as easily removed from an optical fiber contact once it isdisposed within an optical fiber contact connector since a pressureexerted against the coating material 8 within the connector may cause aportion of the coating material 8 to remain within the connector uponremoval of the contact thus requiring that the connector be cleaned. Inany case, the coating material should be substantially transparent atoptical frequencies for which the fiber is to be used, and optimallyshould have an index of refraction which is the same as, or close to,that of the fiber core.

A significant advantage of the invention is that it allows the formationof any desired size of coating material 8 to be applied to an end of anoptical fiber within an optical fiber contact. Specifically, the size ofthe coating material 8 can be made so as to be only slightly larger indiameter than a diameter of either a core or a cladding of the opticalfiber. According to a particularly preferred embodiment, the coatingmaterial 8, due to its small size, is either substantially spherical inshape once formed on the reservoir floor due to surface tension effectsor at least has a dome-like shape. The coating material 8 preferably hasa diameter less than ten times a diameter of the fiber cladding,preferably less than five times the cladding diameter, more preferablyless than three times the cladding diameter, even more preferably lessthan two times the fiber cladding diameter, most preferably about thesize of the cladding diameter, and it can even be formed so as to beonly slightly larger, e.g. 20%, 100% or 200% larger than the corediameter. The invention further includes a coating material size whichis smaller, e.g. by 20% or 30%, than a diameter of the fiber claddingthe coating material ultimately covering the entire end face of thefiber core since upon fiber contact connection to an optical element thecoating material 8 will be flattened out so as to form an ellipticalshaped structure.

The reservoir floor is preferably made of an elastic material, asdescribed, and is also preferably transparent, a thickness of themembrane preferably being less than 1000 um, more preferably less than500 um, e.g. about 400 um, and a material from which it is constructedcan simply be a thin rubber membrane with sufficient elastic force toinsure the get coating is cut upon retraction of the needle.

A further feature of the invention is the provision of a cleaning meansdisposed within the substrate 2 for cleaning an end of an optical fibercontact, and in particular an optical fiber contained therewithin priorto disposing the coating material 8 on the fiber end. The cleaning meansincludes a second reservoir 21 which includes a cleaning pad 22 disposedtherein, the cleaning pad 22 including a cleaning agent. With thisstructure, the contact end is first inserted into the second reservoir21 so as to bring the fiber end in contact with the cleaning agent onthe cleaning pad, the fiber end is then preferentially wiped with anonlinting cloth or similar material, and subsequently the fiber end isthen disposed within the first reservoir 3 so as to dispose the coatingmaterial 8 thereon.

The invention works best for coating fibers having ends which are flushwith their associated contact end surfaces. However, the invention isalso useful with contacts where the fiber end is recessed, preferablyrecessed by a distance less than one cladding diameter.

An additional advantage of the invention is that the coating 8 is notpermanently bonded to the fiber end but yet adheres thereto. Hence, thecoating is readily removable from an optical fiber connector uponremoval of the fiber so that a connector interior can be kept clean andis easily cleanable. Also, the coating can thereafter easily be removedfrom the fiber end by simply wiping the end clean. Hence the coating iseasily disposable and a new coating can easily be applied to the fiberend without the necessity of re-terminating the fiber by additionalcleaving steps, for example.

Finally, the invention is particularly useful for use with multipleoptical fiber connections. FIG. 9 illustrates a rectangular dispenser 31having a plurality of coating material spheres 8 therein. An arrayconnector having a plurality of in-line optical fiber ends 12 isinserted into the dispenser 31, and due to the adhesion propertiesbetween the coating material spheres 8 and the fiber ends 12 uponwithdrawal of the array connector all the fiber ends 12 areappropriately coated, as desired.

Though the invention has been described by reference to certainpreferred embodiments thereof, the invention should not be so limitedand should be limited only the appended claims.

What is claimed is:
 1. A dispenser for dispensing a coating material onto an end of an optical fiber, comprising:means for dispensing an optical fiber coating material, the dispensing means including a base and sidewalls surrounding the base so as to form an optical fiber coating material dispensing platform; and an optical fiber end coating material disposed on the platform and separated from the sidewalls.
 2. The dispenser of claim 1, the sidewalls having an internal perimeter shape which is registrable with an external perimeter shape of an optical fiber contact to which an optical fiber having the end to be coated is secured so that the coating material will be disposed on an end of a core of the optical fiber when the contact is registered with the sidewalls.
 3. The dispenser of claim 2, the sidewalls internal perimeter shape and contact external perimeter shape each being cylindrical.
 4. The dispenser of claim 1, further comprising a plurality of coating materials disposed linearly on the base for a like plurality of fiber ends, the sidewalls being rectangular in shape.
 5. The dispenser of claim 2, the coating material being located approximately within a geometric center of the base, the coating material having a substantially spherical shape and having a diameter less than a diameter of a cladding of the optical fiber.
 6. The dispenser of claim 1, the base comprising an elastic membrane, a top surface of the membrane, the coating material, and the fiber end being made of materials such that the coating material preferentially adheres to the fiber end rather than the top of the membrane.
 7. The dispenser of claim 6, the top surface of the membrane including a release agent, the coating material being disposed on the release agent.
 8. The dispenser of claim 1, the coating material being elastic and having a cone penetration value between 30 and 350 (10⁻¹ mm), and an ultimate elongation greater than 20%.
 9. The dispenser of claim 1, the dispensing means further including a cover having a perimeter secured to a top surface of the sidewalls so as to form a hollow enclosure, the coating material occupying a volume substantially less than a volume of the enclosure.
 10. The dispenser of claim 1, further comprising:a substrate, the dispensing means being disposed within the substrate; and means for cleaning the optical fiber end, the cleaning means being disposed within the substrate adjacent the dispensing means.
 11. The dispenser of claim 10, the cleaning means comprising a reservoir containing an optical fiber end cleaning pad which contains an optical fiber end cleaning agent therein.
 12. The dispenser of claim 1, the dispensing means being sufficiently transparent so as to enable a location of the coating material thereon to be visually confirmed by looking through the floor from an underside thereof. 